The air pressure in vehicle pneumatic tires should be maintained within a particular range to protect against tire damage or failure, and to promote safe and efficient operation of the vehicle. For example, overinflated or underinflated tires may cause tire wear, internal tire damage, increased risk of tire penetration by sharp objects, blowouts and/or reduced vehicle fuel economy. A tire pressure monitoring system (TPMS) can be used to monitor air pressure inside a pneumatic tire and to generate an alert if the tire pressure falls outside of a desirable range for the tire. A TPMS may incorporate a tire pressure sensor placed inside a tire and means for transmitting pressure information detected by the tire pressure sensor to a receiver.
A TPMS may be used for monitoring air pressure in off-the-road (OTR) pneumatic tires used on large off-road vehicles such as mining trucks, construction vehicles or the like. The interior of OTR or other pneumatic tires may have corrosive liquids or gases, due at least in part to the presence of corrosive chemicals which are used to treat the tires to facilitate mounting and dismounting of the tires to wheels. Tire pressure sensors placed inside the tires may be exposed to corrosive liquids or gases which may corrode the sensor components, such as the sensor's electronic components and circuitry. Such corrosion may lead to failure of the tire pressure sensor.
To protect against corrosion (such as may be caused by the corrosive interior of OTR tires), some tire pressure sensors have a housing for encasing the sensor electronic components and circuitry. An opening is provided in the housing, and a filter covers the opening. The filter permits only gases (e.g. the tire's pressurized air), and not liquids, to pass through the opening to a pressure transducer contained inside the housing. However, corrosive gases contained in the tire may pass through the filter, along with the tire's pressurized air, thereby causing damage to the sensor electronic components and circuitry in the housing.
There is a general desire to provide tire pressure sensors which overcome or at least ameliorate these and/or other drawbacks.